The present invention relates to a magnetic disk apparatus, and particularly to a technique to be applied effectively to a-magnetic disk apparatus equipped with a high recording density medium.
In a moving-head magnetic disk apparatus, for example, the magnetic head is moved to the position of an intended track on a magnetic disk which is a magnetic recording medium. The magnetic head is required to move quickly in the radial direction in response to a request of access to specific information recorded on the magnetic disk surface so that the access time is minimized. Accordingly, a voice coil motor of relatively high power is used for the movement and positioning of the magnetic head.
When the voice coil motor, which is fixed on the base, operates under sharp acceleration and deceleration control in response to an access request or the like, the operation causes the magnetic head carriage to vibrate. This vibration creates a bending moment on the magnetic disk apparatus relative to the base, resulting in the occurrence of off-tracking, i.e., the magnetic head moves out of the target track. This is a serious problem when it is attempted to increase the recording density by narrowing the track pitch thereby increasing the number of tracks on the magnetic disk.
The head positioning mechanism of the conventional magnetic disk apparatus which deals with this problem will be explained with reference to FIGS. 10 and 11. FIG. 10 is a perspective view, and FIG. 11 is a partial cross-sectional diagram of the head positioning mechanism.
In the head positioning mechanism, a carriage 13, which has the attachment of a servo head arm 5 for supporting a servo head 2 and a data head arm 4 for supporting a plurality of data read/write heads 3, is fitted rotatably around a pivot shaft 6 as shown by the arrow A through a bearing 12 on an I-shaped carriage block 9. The voice coil motor has its magnet 7 secured on the side surface of the carriage block 9 by screws 11, and the voice coil 8 of the voice coil motor is connected to the carriage 13.
The voice coil motor has the voice coil 8 connected to the carriage 13, which is supported rotatably on the pivot shaft 6, thereby constituting a rotary actuator. The voice coil motor is controlled in accordance with the servo signal provided by the servo head 2, and the data heads 3 are positioned to the intended tracks on the magnetic disk 21.
In this head positioning mechanism, the magnet 7 is clamped between two magnet supports 15 and a bolt 14, and fixed to the base 17 by means of screws 16 through holes 10 formed in the magnet support 15, so that the mechanism has an enhanced rigidity against the bending moment (in the direction shown by the arrow A) at the acceleration and deceleration of the rotary actuator and the vibration is damped by the frictional movement of a damping mass 18 which is placed on the carriage block 9, thereby reducing the bending moment on the carriage 13 against the base 17 (in the direction shown by the arrow B in FIG. 11).